Manufacture of electric heating bodies



, 165.11932. H. w. KURZ 'ununcn'r'ns oF-mncwnic HEATING onnzs Filed sept. 1,' 192s 2 sheets-sheet 1 ATTORNEYS Patented Aug. 16, 1932 UNITED s'rA'rEs PAT-ENT OFFICE HERMANN 4WILHELI KURZ, 0F mmORT-ON-THE-MAIN, GERMANY, ASSIGNOR TO THE FIRE VOIGT HAEI'FNER AKTIENGESELLSCHAFT, OF FRANKl'0I"1'-0N'--'.l`.HE-

e uam, annimmt IANUIACTURE l' ELECTRIC BDIES vApplication lledeptember 1, 1928, Serial No. 308,479, and in Germany September 5, 1927.

The present invention has reference to the manufacture of lelectric heating bodies, in particular heating plates, in which the heat conductor is disposed inside an insulating Il mass. Inthe manufacture of such heating bodies, and especially in the bedding-in of the heat resistances, particularly whensame are yof spiral or similar shape, certain difliculties' with these lates, being perfectly uniform. f

These di culties are avoided by the procform, a's nearl directly or indirectly throu .wa of example. 0

igures 1 to 5 inclusive illustrate sectional ess forming the object of this invention, accordin -to which the said heat conductor, for vexamp e a heating s iral, is first pressed lightly into a loosely eaped insulating material, and further insulating material is then inserted, whereupon the final bedding-in of the heating material is either finished direct under pressure or with the insertion of the said radiation plates. The process here is as follows: On the base plate of a suitable press tool, which is surrounded by a removable ring, insulating mate-rial is first filled in. Then by means o -a special tool, the heat-v ing element, which is constructed in the form `of a heating spiral or in other suitable form,

is pressed in on the surface. Then this tool is removed, the space filled with further insulating material and, in the oase of heating bodies without heating plate, the pressure is completed by means of a flat plate under suitable pressure, or the radiation plate is setin position, and both the heating material and its insulating mass is suitably connected -under pressure with the radiation plate. At the end of this pressing operation, the insulating material is secured. i. e. the converlsion of the insulating material into a fixed as possible unalterable, `is effected by heating the heatin elementy either current.

In the drawings a'suita'ole evice for carrying out the present process is represented by views of an apparatus for carryingout the present process, the various steps of the meth od being successively indicated in'said figures; and Figure 6 is a plan view-of a tool employed for holdin the heat conductor during the process of imbedding the same in the insulating material.

In said drawings, ais the actual pressure block, b is a ring surrounding the saine which can be pressed downwards against the tension of the springs c. d and e are apertures for the introduction of the connecting wires of the heating spiral and f is the loosely heaped insulating mass.

.Figure l shows the separate parts of the pressing device at the moment before the pressin in of the spiral g.VA This operation takes pIace by means of a tool h re resented in Figure 6, which may, for examp e, be provided with two spiral-shaped cut-out portions in which the heating spirals g are inserted. On the `tool k there rests, further, another 'tool ring z'. Pressure is exerted on parts h and by a spring lc. Now, when downward pressure is applied to the plunger Z fitted in the pressure block a, the tool h presses the heating s iral g into the loose insulating material (Figure 2). At the same time,

pressure is transmitted to the tool ring z' under the effect ofthe spring k, so that the tool h simultaneously exerts a downward pressure. In this way the insulating material underneath the members of the tool h containing full material is slightly compressed, and thus any possibility of the heatingl spiral g being displaced in a lateral direction on the pressing-inof the insulatin material is avoided, i. e.the heating spira gis pressed into the mass f at the precise distance which it is given in the tool i by the spiral-shaped cut-out portions. Figure 2 shows the parts ofthe pressing device at |the moment when the first slight ressing-in of the heating spiral is conclu ed. Then the pressing tools h an z' are removed and the' space above the spiral g is'filled with insulating material.' Should a heating element without metallic radiation .plate be made, a flat plate m is set in position and the body compressed (Figure 3) under a correspondingly high pressure. If, on the other hand, the

heating material is pressed into Aa radiation plate fn, then, as shown in Figure 4, the plate n, which can be rovided with wedge shaped rings and suita ly introduced in a lateral direction, is pressed into the material f under a very high pressure. In this case the plate n with its rings presses into the insulating material, While the ring b is compressed. The plate n then forms, with the heating spiral g of the insulating material 7, a comparatively rigid body, as shown in Figure 5.

In order not to damage the connecting wires of the spirals g, these are pushed through the apertures d and e on being introduced into the tool ring la. The construction of the individual tool rings can vary considerably to correspond with the construction of the heating body. The only essential. feature is that the heating spiral g in its insulating material f should first be lightly pressed by the heating body, then filled up again with insulating material, and finally the required rigid heating body is brought into suitable form under pressure.

In the manufacture of heating plates, according to the process hereinbefore described, a comparatively porous and irregular surface is obtained in general. Further, the insulating material used possesses hygroscopic properties which are prejudicial to the lasting uniformity of the heat resistances. To avoid this defect, according to this invention for the lowestlayer i. e. in heatin plates or cast bodies, for the last heaped material, a layer is used Which consists essentially of ceramic material with necessarily low electric insulating properties, but which provides a smooth outside layer capable of resistin detrimental effects and at the same time s uts oif the actual insulating mass from hygroscopic henomena by virtue of its own material. s material for this purpose ceramic masses such as steatite, porcelain or the like can be used` What I claim is:

The process of manufacturing electrical heating bodies, which comprises suitably confining a layer of dry powdered insulating material of uniform densit throughout the depth thereof, then imbedyding an electrical conductive heating body in said dry la er by applying a slight pressure to said bo y and simultaneously slightlycompressinglsaid dry layer for the purpose of preventing said body from being displaced Within said layer, laying a second layer of the same insulating material over the first-mentioned layer, then applying a layer of ceramic material to the second-mentioned layer, applying a heavy pressure to said layers to form said layers into asolid mass and heating said conductor.

In testimony whereof I aix my signature.

HERMANN WILHELM KURZ. 

